Film loop control system for sound motion pictures

ABSTRACT

A film transport control system for a sound motion picture production and sound editing system, comprising a combined motor and transformer which serves to supply power to the apparatus, including power for the projection lamp, to drive a program control shaft that controls operation of the system for photographic processing, projection and rewinding operations, and to drive an incremental film advance pawl. A DC motor drives a capstan, to move the film at uniform speed past a transducer head, under the control of a photocell illuminated at times by a loop formed in the film between the sound head and the projection drive pawl driven by the combined motor and transformer. The photocell controls the motor through a two stage amplifier comprising two filtering capacitors to provide a long time constant control over the average speed of the capstan to reduce wow and flutter.

United States Patent [1 1 Deeran Aug. 27, 1974 FILM LOOP CONTROL SYSTEM FOR Primary Examiner-Samuel S. Matthews SOUND MOTION PICTURES Assistant Examiner-Alan Mathews Inventor: Robert H. Deeran, Derry, NH. Attorney, Agent, or Firm-John W. Ericson [73] Assignee. Selig-old Corporation, Cambridge, [57] S C 22] Filed; J 2 1973 A film transport control system for a sound motion picture production and sound editing system, compris- PP N04 374,637 ing a combined motor and transformer which serves to supply power to the apparatus, including power for 52 us. 01 352/14, 352/180, 352/198, the Projection lamp, to drive a p g control Shaft 22 /42 that controls operation of the system for photographic [51] Int. Cl. G03b 31/00 Processing, Projection and rewinding Operations, and 581 Field of Search 352/14, 72, 159, 29, 180, to drive an incremental film advance p A DC 352 193; 22 30 42 45; 242 133 motor drives a capstan, to move the film at uniform speed past a transducer head, under the control of a 56] References Cited 7 v photocell illuminated at times by a loop formed in the UNITED STATESPATENTS film between the sound head and the PI'OJCCUOD drive pawl driven by the combined motor and transformer. rorr'ssey The photocell controls the motor through a two stage 3236429 M9 E25 226/42 amplifiercomprising two filtering capacitors to pro- 3'597056 8/1971 l' 'fi' 'z 352/14 vide a long time constant control over the average 32637Zl23 1/1972 Jones 226/42 Speed of the capstan to Feduce WOW and flutter- 3,72l,376 3/1973 Christian l0 Claim, 19 Drawing Figures POWER B2 SUPPLY SHUTTER SHAFTS INHIBIT REPLAY n PATENIED M182 71974 sum 01 one;

PATfNIfuauczmm 81m 02 mm V PQK WK mm This invention relates to sound cinematography, and particularly to a novel sound motion picture producing and editing system.

In US. application for Letters Patent Ser. No. 227,080, filed on Feb. 17, 1972 by Edwin H. Land for Photographic System for Processing and Projecting Transparencies, and assigned to the assignee of this application, a motion picture processing and projection system is disclosed with which motion pictures can be processed and projected substantially as soon as they have been exposed. This system makes use of a film cassette containing a strip of film, a supply of processing composition for. the film, and an internally programmed processor responsive to manipulation of the film in the cassette for applying the processing composition to the film after its exposure.

The cassette is adapted to be inserted in a camera, for exposure of the film. After exposure, it is inserted into a film drive and projection system. This system comprises a receptacle shaped to receive the cassette, and cyclic drive apparatus for manipulating the film in the cassette. The film is manipulated in a sequence determined by a signal provided by the cassette that indicates whether or not the film has been processed.

In response to the insertion of a cassette containing unprocessed film, the film drive and projection apparatus manipulates the film in the cassette in a lighttight environment. That movement of the film activates the processor, developing the film to produce a series of fixed, visible, projectable images. Thereafter, the apparatus manipulates the film in an optical system causing it to be projected for viewing. The film is then rewound, for storage and subsequent reuse. Finally, the cassette is ejected. In response to the insertion of a cassette containing processed film, the system simply projects the film, rewinds it, and then ejects the cassette.

It would be highly desirable to supplement a system of the type described in the above-cited application by incorporating the facility for recording sound on the film strip, either as it is being exposed in the camera, or after the images have been processed. Recording a sound track simultaneously with the exposure of the film to produce a satisfactory motion picture requires skills that not everyone possesses. However, once the picture sequence has been produced, it is not a matter requiring unusual talents to select a musical accompaniment, or to provide a descriptive vocal commentary, to add the aural dimension to the visual sequence and thus provide a gratifying entertainment experience not requiring inordinate skill andtalent to produce.

The art of producing sound motion pictures is highly developed. For the professional, it is merely a matter of selecting one of the numerous sophisticated systems available in order to produce almost any conceivable visual and aural experience. For the amateur, however, who does not have unlimited funds, time and professional skills at his command, the essential elements of a satisfying sound motion picture production system are economy, convenience and simplicity. The object of this invention is to extend the capabilities of a sound motion picture processing and projection system of the kind described in the above-cited application to facilitate the addition of a sound track without unduly com- 2 plicating the system, making it inordinately costly, or significantly taxing the skill of the user.

More particularly, the object of my invention is to extend the capabilities of an existing motion picture processing and projection system to enable the user to add and reproduce a sound track without vitiating the basic design concept of the system which enabled it to be reduced to practice in a simple, reliable form. In particular, in constructing a film processing and projection system in accordance with the above-cited application Ser. No. 227,080,-a high degree of interrelation between the requirements of the several elements of the system was sought and attained in order to achieve essentially fully automatic operation without seriously compromising size, weight and reliability.

Perhaps the most fundamental consideration underlying the successful implementation of an automatic system is the choice of the power supply. In the system described in the above-cited application Ser. No. 227,080, the'power supply is basically required to perform three functions. One is to manipulate the film in the cassette to cause it to be processed, to be rewound, or to be projected. A second is to provide energy for implementing the decision-making process that begins when a cassette is inserted in the apparatus.

A third, and surprisingly demanding requirement, is that adequate light be provided for projection of the film after it has been processed. In the latter regard, the state of the art dictates the use of a projection lamp having a relatively low voltage, high current filament for maximum brillance and service life. Since it is obviously desirable to operate any home entertainment system from the conventional volt AC source, some form of transformer for producing the operating voltage for the projection lamp is clearly indicated.

In order to reduce the cost, size and weight of the apparatus required, a combination shaded pole induction motor and transformer was chosen as the key element of the power supply. windings on this combination motor and transformer were employed to energize a DC power supply, to energize a motor shaft to control film advance for projection, to operate a cycle control for the system, and to energize the projection lamp. The result is a very economical system, considering the complexity of its functions, which serves to process, project and rewind film in a cassette inserted in the apparatus. The addition of sound to this system, without making any basic changes in the combination power supply concept, isthe central problem to which the invention here described poses a solution.

Both magnetic and optical methods of recording of sound on film for the production of sound motion pictures are well known in the art. Because it is desired to make the system with which the invention isconcerned susceptible to the addition of sound to the film at any time, or to sound editing, magnetic recording was chosen as the most practical expedient. The reason is that optical recording does not lend itself to selective recording or editing independently of the development of the visual images on the film.

In order to record and reproduce sound on the film, it is also well known that the film must move smoothly and uniformly past the sound transducer, whereas an intermittent motion at the projection gate is essential. In order to produce these different types of film motion in the same film without interference, it is common to provide a capstan for driving the film past the sound head, and a film drive pawl for intermittently moving the film past the film gate, separated by a loop of film which is intermittently shortened and lengthened to take up the instantaneous differences in speed of the film at the film gate and at the sound recording station.

In order to maintain synchronism between the picture and sound, it is conventional to provide a constant speed mechanism for controlling the capstan, and to control the average speed of the film drive pawl in accordance with the speed of the capstan motor to make the average film speed the same past the sound station and the film gate. It has been proposed to establish a constant average speed at the film drive pawl, and to use this speed as the standard for controlling the capstan, but that is not ordinarily done because the imposition of a conventional speed control on the capstan motor would result in intolerable wow and flutter in the recorded and reproduced sound.

However, in the self-processing motion picture system with which the invention is concerned, it is quite undesirable to regulate the speed of the combination motor and transformer, which, among other things, drives the film advance claw. The reason is that any conventional regulation of the speed of this combined motor and transformer would also regulate both the RMS and the peak-to-peak values of the voltages provided to the DC power supply and to the projection lamp. Variations in the RMS voltage would affect the brillance of the lamp in a noticeable manner, whereas variations in the peak-to-peak value of the AC voltage supplied to the DC power supply would result in regulation of the DC control voltages developed, which would necessitate expensive voltage-regulating equipment that would be undesirable additions to the cost and complexity of the apparatus. Accordingly, a particular object of the invention is to facilitate the synchronization of sound and picture by regulating the capstan drive rather than the film pawl drive.

Briefly, the above and other objects of the invention are attained by the construction of a novel sound motion picture production and sound editing system in which the projection lamp, the DC power supply, and the film pawl drive and programming shaft are all supplied with energy by a combination motor and transformer which is not regulated in speed. The DC power supply serves to energize a capstan drive motor which is controlled in response to the length of a loop of film between the sound station and the projection station by a very long time constant servomechanism. The servomechanism adjusts the average speed of the capstan to the average speed of the film drive pawl sufficiently rapidly to take care of normal fluctuations in line 'voltage causing variation in the speed of operation of the combined motor and transformer, without requiring constant speed regulation of either drive. The result is an effectively constant speed drive for the capstan which is not characterized by unacceptable degrees of wow and flutter, coupled with a lamp which is essentially characterized by a sufficiently constant brillance.

The manner in which the apparatus of the invention is constructed, and its mode of operation, will best be understood in the light of the following detailed description, together with the accompanying drawings, of an examplary embodiment thereof.

IN THE DRAWINGS FIG. 1 is a schematic perspective sketch of an audiovisual system comprising a replaceable film cassette and a sound motion picture producing and sound editing system in accordance with the invention;

FIG. 2 is a schematic elevational view, with parts shown in cross-section and parts broken away, of the producing and editing system of FIG. 1, taken substantially along the lines 22 in FIG. 1;

FIG. 3 is a schematic fragmentary perspective sketch of a portion of a cassette receiving receptacle in the producing and editing system of FIG. 1, taken substantially along the lines 3-3 in FIG. 1;

FIG. 4 is a schematic plansketch, with parts omitted, parts shown in cross section, and parts broken away, of a film cassette in accordance with the invention, shown in conjunction with a sound array forming a part of the producing and editing system of FIGS. 1, 2 and 3;

FIG. 5 is a fragmentary schematic plan sketch, with parts broken away, of a film strip forming a part of the cassette of FIG. 1;

FIG. 6 is a schematic elevational cross-sectional sketch of a film drive mechanism forming a part of the apparatus of FIG. 1, shown in conjunction with a portion of a cassette cooperating therewith;

FIG. 7 is a schematic fragmentary plan view, with parts shown in cross section, parts omitted, and parts broken away, illustrating a portion of the producing and editing system of FIG. 1;

. FIG. 8 is a fragmentary schematic view of portions of the cassette and sound array of FIG. 4, showing elements of the sound array engaged with the film in the cassette;

FIG. 9 is a fragmentary schematic plan view, with parts omitted, parts shown in cross section, and parts broken away, of a blinder mechanism forming a part of the apparatus ofFIGS. 2 and 7, in one position assumed during its operation;

FIG. 10 is a fragmentary schematic perspective sketch of a locating pin latching mechanism forming a part of the apparatus of FIG. 7;

FIG. 11 is a fragmentary schematic plan sketch, with parts omitted, parts shown in cross section, and parts broken away, of a locator pin and its actuating mechanism forming a part of the apparatus of FIG. 7;

FIG. 12 is a schematic cross-sectional elevation of a portion of the apparatus of FIG. 7 taken substantially along the lines [2-12 in FIG. 7 and showing a pressure plate lifting mechanism in its cooperative relationship with a cassette;

FIG. 13 is a schematic block and wiring diagram of a cam shaft and associated paratus of FIG. 7;

FIG. 14 is a schematic block and wiring diagram of control circuits forming a part of the apparatus of FIGS. 1 and 7;

FIG. 15 is a schematic elevational view of a recording, replay and editing control forming a part of the system of FIG. 1;

FIG. 16 is a fragmentary schematic view of a portion I of the apparatus of FIG. 15, with parts omitted and parts forming part of the ap- FIG. 18 is a schematic fragmentary view of another portion of the apparatus of FIG. 15, taken essentially along the lines 18-18 in FIG. and

FIG. 19 is a schematic wiring diagram of sound recording, erasing and reproducing apparatus forming a part of the producing and editing system of FIG. 1.

FIG. 1 shows the external cooperative aspects of an audiovisual system embodying the invention. The basic elements of this system are a cassette 1, adapted to be inserted in a pocket 2 formed in the outer housing 3 of a sound motion picture producing system generally designated 4. A translucent viewing screen 5, on which projected images at times appear, is mounted at the front of the housing 3.

As best shown in FIG. 2, the pocket 2 has a floor 6 on which an aperture plate 7 is mounted. The aperture plate 7 is adapted to extend into the cassette such as l and there register with the film in the cassette. Light, supplied in a manner to be described, passes through the film, and thence over a path traversing a suitable framing aperture in the aperture plate 7, a cooperating recess in the floor ,6, a blinder housing 8, to be described, and a conventional shutter 9, to a lens 10. The lens focuses an image of the portion of the film selected by the framing aperture on a mirror 11, whence it is reflected to the screen 5.

A speaker 12 is mounted in the housing 3 of the system 4 at the front and below the screen 5 as indicated schematically in FIG. 2. The speaker 12 is at times energized to produce sound recorded on the film in the cassette 1 in a manner to be described. For that purpose, a sound array generally designated 13 is mounted in the housing 3 just behind the pocket 2, and communicates with a cassette in the pocket 2 through an aperture 14, FIG. 3, formed in an end wall 15 of the pocket 2. The sound array 13 generally comprises a combined recording, playback and erasing head 16, and'a film drive capstan 17, mounted on a suitable support generally designated 18, and to'be described in more detail below, so that it can be moved into and out of engagement with film in the cassette 1.

As shown in FIG. 1, an editing control unit generally designated 19 is removably mounted on a stand 20 having a base 21. The control unit 19 comprises a microphone 22 mounted in a suitable housing 23 adapted to g be grasped in the hands of the user, and provided with a replay push button IPB and a two-position recordlisten push button RPB, constructed and arranged in a manner to be described in detail below. The unit 19 is electrically connected to the base 21 of the apparatus by means of a flexible cable 24, which may be continuously connected to a cable 25 that electrically connects the remote assembly to the housing 3. A volume control 26 mounted on the exterior of the housing 3 enables the user to select the volume produced by the speaker 12 in a manner to be described.

As shown in FIG. 1, the cassette 1 is provided with a number of light-baffled openings 30, 31, 32, 33 and 34. These openings expose parts adapted to cooperate with corresponding parts of the film drive and projection system to perform various functions in the eassette. Thus, a drive sprocket formed on the takeup reel is accessible through the opening 30. A similar drive sprocket formed on the supply reel is accessible through the opening 31. Projection light is at times admitted to the cassette through the opening 32-. A stop can enter, to brake a snubber roll forming a part of the cassette, through the opening 33. The opening 34 serves to admit a locating pin, forming a part of the motion picture producing and sound editing system to latch the cassette in position for manipulation, and to energize the producing and editing apparatus in a manner to be described.

A flange 35 is formed on the upper end of the eassette 1. This flange aids in grasping the'cassette while inserting it in, or removing it from, the pocket 2. It also helps to fix the cassette in position in the producing and editing system, by engagement with the rim of the pocket 2.

Referring to FIG. 3, parts adapted to enter the openings in the cassette 1 just described at times enter the pocket 2 through corresponding openings in the side wall 36 'of the pocket. Drive sprockets for the supply and takeup reels are adapted to enter through openings 37 and 38, respectively. A light beam for projection enters through an opening 39. The locating pin enters through an opening 40. The snubber roll stop enters through an opening 41.

In addition to the aperture plate 7 described above, the actuating arm of a normally open switch S1 is movably mounted on the floor plate 6. This switch is adaptedto be closed when a cassette is inserted in the pocket 2, for purposes to appear.

A foot pedal 42 is movably mounted in the pocket 2 to be depressed by the insertion of a cassette. The foot pedal is connected to an actuating arm extending through the floor plate 6, as will be described below.

FIG. 4-shows, in part fragmentarily and in part schematically, the pertinent elements of an internally programmed cassette 1 adapted for use in the system of the invention. Except as modified ina manner to be described, the cassette may be constructed in the manner described in detail in the above-cited US. application Ser. No. 227,080.

The cassette comprises a housing formed of any suitable opaque material such as metal, plastic, or the like, and preferably manufactured in two cooperating parts.

The housing parts comprise a base plate 43 formed integral with side walls 44, 45, 46 and 47. The base plate 48 extends across the base of the side walls, and comprises one side of the housing, The walls 44, 45, 46 and 47 extend at least in part about the periphery of the base plate 43, and cooperate with interfitted walls, shown and described in the above-cited U.S. application Ser. No. 227,080, formed integrally witha cover generally designated 50. The cover plate 50 completes the upper side of the housing as seen in'FIG. 4.

When the cover 50 is placed in position, it may be formed integral with the base plate and side walls by heat sealing, or by a suitable adhesive, or the like. If of metal, the inter-fitting parts may be interlocked with cooperating detents formed therein, in a manner coitventional and well known to those skilled in the art.

The base and cover parts form, when assembled, the end flange 35 that serves to support and locate the eassette 1 in either a camera, or in the motion picture producing and editing system of FIG. 1.

Rotatably disposed within the cassette housing is a supply reel generally designated 51. The reel 51 is provided with an upper flange 52 and a corresponding lower flange, not shown, to guide a film strip 53 as it is wound about the spool portion of the reel 51, not

shown, to which one end of the film strip 53 is attached.

A sprocket schematically indicated at 54 may be formed integral with the reel 51 to adapt the reel to be driven about its axis of rotation. Access to the sprocket 54 may be provided through the aperture 31 in the cover plate 50 (FIG. 1), light-baffled by suitable conventional annular flanges, such as 55, formed on the upper surface of the flange 52 (FIG. 4), and cooperating with corresponding coaxial flanges, not shown, on the inner side of the plate 50. The lower flange of the reel 51 may be formed in a conventional manner with a cylindrical axial opening to receive a cooperating axle, not shown, formed integral with the base plate 43.

Initially, the film 53 is' in its unexposed state and coiled primarily about the supply reel 51. It is shown in FIG. 4 in the position assumed as it nears the end of its movement away from the supply reel, as toward the end of exposure in a camera, in which it is nearly exhausted from the reel 51.

In its path from the supply reel 51, the film 53 first encounters a bobulator roll 56. The film engages a portion of the periphery of the bobulator roll, as shown, and passes therefrom into a suitably light baffled sound recording and reproducing station generally designated 57. The sound station terminates with the passage of the film 53 over a backup roller 58. The film is at times engaged by the capstan 17 acting through the film against the roller 58, whereupon the film is driven smoothly through the sound station, as will appear.

The roller 58 is journalled for rotation in the cassette housing. From the roller 58, the film 53 passes through film processing means, to be described below. In addition to the apparatus for processing the film in a manner to be described, the film processing means comprises a signal generator for producing an external condition signal on terminals schematically indicated at 59 and 60, to indicate whether or not the processing means has been actuated.

Beyond its path through the film processing means, the film 53 extends through a conventional lightbaffled aperture schematically indicated at 61 and forming a portion of a film gate in the housing. The film 53 reenters the housing through a second light-baffled aperture generally deisgnated 62 and comprising a second portion of the film gate. I

The film 26 next passes over a conventional snubber roll, generally designated 63, and finally passes to a takeup reel generally designated 64, comprising a spool portion to which the takeup reel end of the film is connected, and about which the film is wound as suggested in FIG. 4.

In addition to parts corresponding to those parts described in connection with the supply reel 51, the takeup reel 64 comprises an external upper flange 65 protruding beyond the maximum radius of the film 53 when substantially stored on the takeup reel. On the flange 65 is formed a suitable drive sprocket 66, by means of which the film can be selectively advanced in a manner to be described.

The bobulator may be of any conventional construction suitable for the performance of the known function of isolating the film drive pawl associated with the camera from the inertia of the supply reel 51. However, it is preferably of the form shown, in which the bobulator roll 56 is journalled on a pin for rotation by the film.

The pin 70 is formed integral with a support 71 of plastic or the like. The support 71 is journalled to the base plate 43 by means of a pin 72 formed integral with the base plate, and biased by a spring 73 formed integral with the support 71. The spring 73 acts against a post 74 formed integral with the base plate 43. The bobulator roll 56 can thus both rotate about the pin 70, and move backwards and forwards in the directions of the double arrow, shown in F IG. 4.

The bobulator roll responds to increases orfdecreases in the tension of the film 53 by temporarily shortening or lengthening the film path, respectively. Such changes in film tension are produced by the actuation of the film drive pawl in the camera, and aredetermined by the inertial forces exerted by the supply reel 51, together with the larger or smaller supply of film that may be on it at any given time. By that arrangement, as the film is advanced incrementally by the pawl associated with the camera, it can rapidly move the bpbulator roll against the spring 73 without immediately affecting the supply reel, which can then more or less gradually allow the bobulator roll to relax while supplying the segment of film taken by the pawl. As mentioned above, the film is driven smoothly through the sound station by the capstan 17, so that the bobulator functions only as an idler in the motion picture producing and sound editing system of the invention.

A lighttight shield around the film gate formed by the apertures 61 and 62 is formed by a wall portion 75 formed integral with the base plate 43 and made integral with the cover plate 50 after assembly of the parts in the manner described above. An exposedchamber behindthe film 53 is thus formed for the purpose of admitting projection light.

The apparatus for this purpose is conventional, and will only briefly be described. In short, it comprises a prism generally designated 76 and comprising a mirror, not shown, but disposed at 45 to the plane of FIG. 4. As schematically indicated, the prism 76 is mounted between extensions 77 formed on the wall 75.

Light enters the cassette through the port 32 formed in the cover plate 50 in directions normal to the plane of FIG. 4. The mirror in the prism 76 directs this light downwardly through the film 53 in the film gate for the projection of images on the film through the lens 10 (FIG. 2).

Also disposed in the chamber bounded by the wall member 75 and the film passing through the film gate is a conventional pressure plate 78, located between the prism and the film, and biased by a spring 79 into engagement with the film. The spring 79 is supported and retained by suitably shaped extensions of the support wall 75, as shown. I

The pressure plate serves in the conventional manner to cooperate with av camera, by locating the focal plane of the film during exposure. An aperture, not shown, is provided in the pressure plate 78, to pass light entering through the prism assembly 76 through a selected frame of the film 53, after the film is processed in a manner to be described. It is preferred that the aperture in the pressure plate be somewhat larger than the frame to be projected so that the aperture in the aperture plate 7 (FIGS. 2 and 3) serves as the limiting aperture bounding the projected frame.

The snubber roll 63 may also be of entirely conventional construction. As illustrated, it is provided with a hub portion schematically indicated at 82 that is adapted to protrude through the (suitably light-baffled) aperture 33 in the cover panel 50 for engagement by a stop member, comprising a part of either the-camera or of the motion picture producing and editing system. The stop member engages the snubber roll when the film is to be incrementally advanced by a pawl for exposure or projection purposes. The cooperation between the snubber roll 63 and the takeup reel 64 is conventional, but will be briefly described.

The drive sprockets 54 and 66 of the supply and takeup reels 51 and 64, respectively, are adapted to be engaged by corresponding drive sprockets comprising a part of a camera, or of the producing and editing apparatus to be described. In the producing and editing apparatus, both supply and takeup reels are adapted to be driven through slip clutches. In the camera, only a drive for the takeup reel need be provided. This drive comprises a slip clutch connected to a sprocket driving the takeup reel drive sprocket 65, in cooperation with a drive pawl for sequentially engaging a series of the sprocket holes 38 formed in the film 26, along a portion of the edge of the film in the film gate between the apertures 60 and 61.

When the snubber roll 62 is stopped by engagement of the hub 82 as described above, operation of either the camera or of the production and editing system to incrementally advance the film towards the takeup reel, by engagement of a pawl with the sprocket holes the film is rewound onto the supply reel, the snubber roll 63 is disengaged and acts as an idler. As will ap-' pear, that may occur either during the processing of the film while rewinding, or during subsequent rewinding of the processed film after projection.

The film processing means may be as described in the above-cited U.S. application Ser. No. 227,080, except as modified in a manner to be described. As shown in FIG. 4, the apparatus generally comprises wall means comprising portions of, or formed integral with, the base plate 43 and the cover plate 50, which serve to guide, support and house the various elements of the processing apparatus to be described. These walls form an outer film composition containing housing generally designated 83, defining a chamber in which there is mounted an initially sealed container of processing composition as'fully described in the above-cited U.S. application Ser. No. 227,080. The container 83 communicates with a coating nozzle generally designated 85. These elements are mounted above the plane of the film 53. I

Principally located below, but in part surrounding, the film 53 is a pressure pad generally designated 86. The pressure pad is acted on by a spring, generally designated 87, as fully described in the above-cited U.S. application Ser. No. 227,080.

The basic elements of the processing station further comprises a combined metallic pressure pad deflection can and nozzle closure valve assembly generally designated 88, and the pair of electrical terminals 59 and 60 mentioned above. The terminals 59 and 60 are bridged by the valve assembly 88 before the film is processed to provide a low impedance electrical signal. The valve assembly 88 is moved after the film is processed to open the circuit path between the terminals 59 and 60 to produce a high impedance between the terminals 12 thereafter, as fully described in application Ser. No. 227,080.

A pod of processing composition within the container 83 is initially sealed by one end of a tear-tab generally designated 89. The tear-tab 89 extends from sea]- ing engagement with the plastic pod of processing composition in the container 83, out through a suitable slot in the container 83, and over a roller 90 in the cassette housing to an end 91 connected toa release arm generally designated 92.

The release arm 92 may be formed of thin sheet spring metal, bent over at one end 93 to form a hook adapted to engage one of a set of teeth 94 formed on the flange 52, and corresponding teeth formed on the lower flange of the supply reel 51. The arm 92 is secured at one end to a pin 95 that is adapted to slide in curved guide slots such as 96, one formed in-the base plate 43, and the other, not shown, in the cover plate 50. A hook 97 on the release arm 92 extends through a suitable aperture in the tear-tab 91. When the supply reel is rotated counterclockwise as seen in FIG. 4, as during exposure .of the film in the camera, the hook 93 formed on the arm 92 is not engaged by the teeth 94, but is simply brushed up into engagement with a fixed support 98 secured to the base plate 43, On the other hand, when the supply reel 51 is first rotated clockwise as seen in'FIG. 4, as to rewind the film on the supply reel, one of the teeth 94 catches the book 93 and drives the arm 92 downward under the guidanceof the slots 96, pulling the tear-tab 89 partly out of the container 83 and releasing the processing composition in the manner fully described in the above-cited copending application Ser. No. 227,080. The arm 92 will carry the teartab down until it is moved out of engagement with the supply reel 51 as the slot 96 diverges from the path of the teeth 94. This arrangement replaces the more complex mechanism described in the cited application Ser. No. 227,080, and'relies on the fact that once the film is exposed, it will' not be rewound on the supply reel until it is desired to process it.

As indicated, the end wall 44 of the cassette 1 is modified by the provision of a first aperture 99, adapted to receive the sound head 16, and a second aperture 100, adapted to admit the capstan l7 and to permit the escape of a small loop of film in a manner to be described. A container 83 and walls such as 75 in the lower side of the cassette housing serve as light shields for the openings 99 and 100 over that region of the eassette. Additional light baffles suggested as ribs 101 and a wall 102 defining the upper end of the sound station 57 serve to provide light baffles for film beyond that station in the upper directions. I

A backup spring generally designated 102 is mounted behind the film in the sound station 57. The spring is formed with one end bent over as indicated at 103 and there secured to the base plate 43. An extending arm 104 of the spring carries a pair of raised film engaging portions 105 and 106 that serve to receive and support the film 53 as the head 16is moved into engagement with it in a manner to be described. Spacing of the raised portions 105 and 106 causes a desirable partial wrapping of the film 53 around the sound head 16.

As in the photographic system described in US. application Ser. No. 227,080, the system of the invention makes use of a photofinishing process in which the strip of film 53, following exposure in the camera, is contacted with a single processing composition to form a finished transparency from the latent image or images formed on the film during its exposure. In order to provide sound recording and reproducing capabilities, a magnetic sound track is provided along one or both edges of the film, as will next be described with reference to FIG. 5.

As shown in FIG. 5, the film strip 53 comprises a leader 110 terminating at an end formed with an aperture such as 111. The aperture 14 serves to connect that end of the film to the takeup reel 64.

Behind the leader, which may be in the neighborhood of 18 inches in length, there is a strip 112 of photographically useful film, upon'which projectable images may be formed. The strip 112 may be, for example, approximately 50 feet in length for 8 mm film.

Following the photographically useful portion of the film is a trailer region generally designated 113. The trailer 113 terminates at another end formed with an aperture 114 by means of which that end of the film is adapted to be connected to the supply reel 51.

The film 53 may comprise a base of any suitable transparent material of the kind conventionally used for film bases. On this base is applied, at least over the central portion of the photographically usable length of the film 112, an emulsion comprising a photosensitive coating, whereon a series of latent images illustrated by a series extending from a first frame 115 to a last frame 116 may be formed with a camera. The photosensitive coating is preferably of one of the forms, next to be described, which can subsequently be processed to form a projectable image on the film base.

Photosensitive coatings usable in the practice of the invention may be of any conventional variety adapted to be developed by a monobath processing composition to form a positive transparency suitable for projection. In particular, a currently preferred embodiment of the invention makes use of a film structure, which, upon the base, comprises a photosensitive layer including both a photosensitive negative emulsion and an imagereceiving layer to which a positive image may be transferred by diffusion during development without necessitating the subsequent removal of the emulsion containing its developed negative image. This highly desirable feature is made possible by a developed negative image having low-covering power.

In typical silver transfer reversal processes for the projection of black and white images, a silver halide developer and a silver halide solvent are applied in an aqueous alkaline solution to a photoexposed silver halide emulsion stratum, where they develop exposed silver halide to silver, and react with unreduced silver halide to form a soluble silver complex. This complex, in order to form a positive print, is transferred and reduced to silver on a silver-receptive stratum upon which the silver halide stratum has been superposed.

In one practice, in the completion of this process, the silver-receptive and silver halide strata have been separated in order to render the positive print visible. However, as indicated above, the positive print may be rendered visible without separation of the silver halide and the silver-receptive strata. For example, the silverreceptive stratum may be so constructed as to provide an unusually vigorous silver precipitating environment which causes the silver deposited upon it, in comparison with silver developed in the silver halide stratum, to possess very high covering power, i.e., opacity for a given mass of reduced silver. If the silver halide is in such a concentration as to give rise only when fully developed to a predetermined low maximum density, and if the silver complex is reduced to silver in a vigorous silver precipitating environment, the resulting negative and positive prints in superposition provide a' composite print that presents a good image for projection purposes so long as they are contained on a transparent support. Since the silver halide stratum and the-silverreceptive stratum need not be separated, an overall simplification of the silver transfer reversal process is achieved.

A composite film assembly of this type, as well as processing compositions for producing a'fully developed black and white image without the necessity of removing the developed negative image after processing, are shown in US. Pat. No. 2,861,885 to Edwin H. Land, which issued on Nov. 25, 1958, for Photographic Processes and, Products. Other composite film assemblies capable of producing developed full color images without the necessity of removing the developed emulsion are shown in US. Pat. Nos. of Edwin H. Land, 2,726,154, issued Dec. 6, 1955 ,for Photographic Product, and 2,944,894, issued July 12, 1960, for Photographic Processes Utilizing Screen Members.

It should be noted that the invention is not directed to the chemistry by which images are developed in a photosensitive emulsion and transferred to an image receiving stratum. However, in the practice of the invention, whether the film employed is black and white or color film, at the present time the preferred embodiment of the invention employs film of a type not requiring the removal of a negative emulsion after it is developed.

Referring again to FIG. 4, the film 53 is formed along one edge with sprocket holes such as 117 at regular intervals adapted to cooperate with a drive pawl, in a manner to be described, in either camera or projector, for incremental advancement of the film. The series of sprocket holes 117 adjacent the trailing end of the film may be interrupted by a first elongated sprocket hole 118. This elongated hole. 118 may span, for example, two of the sprocket holes 117.

Further along the film in the direction of the supply reel end, the series of sprocket holes 117 is again interrupted by a second elongated sprocket hole 119, longer than the sprocket hole 118 and, for example, spanning three of the sprocket holes 117. As will appear, the first elongated sprocket hole 118 establishes an exposure end point in the camera, whereas the second sprocket hole 119 determines a film takeup termination point in the producing and editing apparatus to be described.

Basically, termination of film advance at the first elongated sprocket hole 118 is attained by the use of a single drive pawl in the camera, which sequentially engages the sprocket holes 117 to advance the film by one frame length in a conventional manner. .Toward the end of each such advance stroke, as is conventional,

the pawl is cammed down out of engagement with the film. When the single pawl engages the elongated aperture 118, the camming down movement occurs before the film engages the leading edge of the elongated hole. The pawl may cycle repeatedly thereafter without further advance of the film. This serves to effect a termination of film advance for the purposes of exposure adjacent the end of the region of photographically useful emulsion, to alert the photographer, by the somewhat different sound produced when the pawl skips the film, that his cassette should be replaced.

The film drive system for projection purposes is provided with a double pawl, comprising two integral pawls spaced apart by one frame length, each pawl being of the same shape as the single pawl in the camera. When the first elongated aperture 118 is encountered, the leading pawl of the pair serves to engage the leading edge of the aperture'1l8 to cause the film to be advanced without interruption. For normally spaced sprocket holes 117, both of the pawls engage the film in sequential sprocket holes. However, when the second elongated sprocket hole 119 is encountered, the pawls will pass through it without film engagement, and thereby terminate film advance in the same manner as did the single pawl upon engagement of the double length sprocket hole 118.

Formed on the trailing end 113 of the film 53, beyond the exposure advance termination portion just described in the direction of the supply reel end of the film 53, in a detent engaging element here shown as an aperture 120 formed in the film, adjacent which a projecting bump 121 is formed, as by pressure, heat and pressure, or the like. The edge of the bump 121 forms a hook adapted to engage a detent in the form of a pro: cess control actuating element, to be described, as the film is moved with respect to the detent in the direction of the takeup reel.

Formed on the leader end 110 of the film 53 is another detent engaging means, here shown as an aperture 124 in the central region of the film. This aperture serves to actuate the valve member 88 forming apart of the processing apparatus described above, for purposes to appear. I

Formed on the sides of the film 53, on the base side opposite the side on which the emulsion is coated, are a pair of side rails 122 and 123. At least the rail 123 is coated with a conventional ferromagnetic recording medium so that the rail 123 serves as a soundtrack for recording and reproduction. The rails 122 and 123 protrude slightly above the surface of the film 53, and serve two basic purposes in the system of the invention. First, when the fluid is processed as to be described, it is initially wet over the useful emulsion region as it is transferred from the processing station' to the supply reel. The rails serve to keep the wet surfaces of the emulsion from contacting the dry base surface of the film as it is wound onthe reel. The use of the rail 123 as a recording surface also makes it possible to maintain contact between the sound track and the transducer head without exerting pressure on the emulsion side of the film.

A capstan wear pad 125, of plastic or the like, is preferably cemented to the trailing end 113 of the film behind the bump, on the side where the rails 122 and 123 are located. This wear pad 125 prevents the capstan 17 from wearing a hole through the film 53 under conditions to be described.

The manipulation of the film in the cassette 1 to process it after it has been exposed is fully described in the above-cited copending application Ser. No. 227,080. However, in order to visualize this process in conjunction with the sound recording and reproducing features of the system of the invention, it will next be briefly described with reference to FIGS. 1 5.

Referring to FIG. 4, it will be assumed that an initially unexposed strip of film 53 stored primarily on the supply reel 51 has been exposed in a camera, so that it has been advanced onto the takeup reel 64 to the exposure termination point determined by the first elongated sprocket hole 118 in the film (FIG. 5). The tear-tab 89 and its release mechanism will be in the positions shown in FIG. 4, with the hook 93 against the stop 98.

Next, assume that operation is continued by further rotation of the takeup reel 64 counterclockwise, as

I seen in FIG. 4, to bring the film 53 farther onto the takeup reel. During this rotation, the supply reel 51 will move counterclockwise in FIG. 5, causing the teeth 94 to pass the hook 93 without effective engagement therewith. I

FIG. 4 shows the parts of the coating station in their initial position, which is maintained during exposure of the film and during a'portion of the first increment of motion just described, from the exposure termination point toward the second termination point in which the film is substantially exhausted from the supply reel, and in which the second elongated sprocket hole '119 in FIG. 5 will be encountered. During the interval of travel between those .positions, .and priorthereto, the cam and nozzle closure plate assembly 88 is detachably held in place in the manner described in copending US. application Ser. No. 227,080, and a film engaging hook 142 formed on the assembly 88 is lightly engaging the base of the film 53.

The pressure pad 86 is initially held inplace by engagement of an integrally formed hook 143 with a detent formed on the end of the spring 87. In that position, the end of the pressure pad 86 lightly engages the base of the film 53 and ears 144 formed on the pressure pad are in engagement with a ledge formed on a wall segment 145 formed integrally with the wall The parts of the coating station will remain in the position shown in FIG. 4 until, during the further advance of the film 53 towards the takeup reel, the film engaging bump 121 approaches and engages the end of the pressure pad 86. When that occurs, near the second termination point established by the second elongated hole 119 in the film (FIG. 5), the bump 12 1 will move the pressure pad to the left in FIG. 4, to a position in which the ears 144 have moved out of engagement with the ledge on the wall 145, and upwardly under the influence of the spring 87. The pressure pad 86 will swing up into engagement with the film 26 and carry the emulsion side of the film into coating engagement with the nozzle 85, as described in the above-cited copending application Ser. No. 227,080.

Next, assume that the first rewind operation is begun, by rotating the supply'reel 51 clockwise in FIG. 4, to advance the teeth such as 94 towards the book 93 on the release arm 92. Further clockwise movement of the reel 51 will cause the teeth 94 to drive the release arm 92 downwardly and to the left in FIG. 4, pulling the tear-tab 89 to release processing composition to the coating nozzle 85. The composition will then be uniformly coated on the emulsion side of the film 53.

The coating operation will continue as the film is rewound onto the supply reel until the processing composition is substantially exhausted, and the film is stored substantially all on the supply reel 51. Toward the end of that operation, the aperture 124 (FIG. 5) will approach and engage the hook finger 142 formed on the valve and cam assembly 88.

As the film 53 continues to moveonto the supply reel, engagement of the aperture 124 in the film with the spring arm 142 will carry the cam and valve member 88 to the right of the position shown in FIG. 4, bringing cams formed on the member 88 into contact with the pressure pad 86 in the region of the ears 144, with the cam assembly 88 being guided by the ears 144, as the assembly 88 moves to the nozzle closing position.

Movement in this direction will continue to move the assembly 88 to the right, as it goes to a position in which the end of the valve assembly 88 closes the nozzle 85. The cam assembly 88 and pressure pad 86 are then latched in a final position as described in application Ser. No. 227,080.

During its movement from the position shown in FIG. 4 to the final position just described, the cam and valve assembly 88 disengages the contacts 59 and 60, and thus provides a signal indicating'that the film has been processed.

FIG. 6 schematically illustrates the film advance pawl mechanism in operative relation to the film 53 in a cassette I inserted in the pocket 2 of the producing and editing system (FIG. 3), with the film gate in registrywith the aperture plate 7. The apparatus comprises a pair of film drive pawls 127 and 128 formed on a lever generally designated 129. The pawls 127 and 128 are adapted to engage sequential sprocket holes 117, to advance the film incrementally. For that purpose, the lever 129 is pivoted as indicated at 130 to a crank arm 131. The crank arm 131 is fixed to a shaft 132 that is at times driven synchronously by an AC motor, to be described.

As shown, the lever 129 passes through a suitable aperture 133 formed in the-floor plate 6, and thence through a slot 134 in the aperture'plate 7 into engagement with the film. An end 135 formed on the lever 129 rides on a pin 136 secured to the floor plate 6. Thus, as the crank 129 rotates, the pawls 127 and 128 drive the film 53 to the left in FIG. 6 until they are brought down out of engagement with the film in response to rotation of the crank arm 129. Thereafter, the pawls are brought up beneath the plane of the film, as suggested by the dotted lines in FIG. 6, back to a position in which they can engage the next pair of sprocket holes 117, and then undergo another advance stroke.

A projection 137 formed on an extension 138 of the hub of the crank arm 131 is adapted to releasably engage a detent 139 urged against the hub 138 by a spring 140 compressed between the detent 139 and a fixed support 141. That causes the pawl to stop in the dotted line position, out of engagement with the film, when the drive for the shaft 132 is disengaged in a manner to be described.

As described above, when the pawls 127 and 128 engage an elongated sprocket hole such as 118 in FIG. 4, the film will continue to be advanced. However, when a more elongated sprocket hole, such as 119 in FIG. 5, is encountered, having a spacing equal to three of the sprocket holes 117, both pawls 127 and 128 will fail to engage the film, and film advance will cease, even though the shaft 132 continues to rotate.

Further details of the motion picture producing and sound editing system will next be described with reference first to FIG. 7. As there shown, the pocket 2 that is adapted to receive the cassette described above is, in part, formed in the housing 3 by two walls described above; i.e., the floor plate 6 and the wall 36 normal thereto, through which certain cooperating parts of the system extend. The pocket 2 is further defined by an end wall 148 and a side wall 149 opposite the wall 36. As described above in connection with FIG. 3, there is an end wall segment 15, not shown in FIG. 7, opposite the end wall 148. Along the wall 149 are mounted a pair of suitably insulated contacts 150 and 151 that are adapted to engage the contact terminals 59 and 60 formed on the cassette.

The aperture plate 7 referred to above that is mounted on the floor plate 6 is shown in FIG. 7 to comprise a framing aperture 152 that defines the margins of the portion of the film in the cassette to be projected. Beside this aperture 152 is the slot 134 through which the film drive pawl, described above, is adapted to protrude for engagement with the film in a cassette in the pocket 2. Another symmetrical pair of slots 153 and 154 are formed in the aperture plate 7. There slots are adapted to receive a pair of pressure plate raising arms, to be described, which serve at times to disengage the pressure plate 78 of FIG. 4 from the film 53, for purposes to appear.

A floor plate 155 is formed integral with the housing 3, coplanar with the floor-plate 6 and normal to the wall 36. On this plate 155 are mounted most of the operative parts of the system to be described.

Energy for the system is arranged to be supplied from a suitable source of alternating current, such as a 60Hz, 120 volt source, connected to a pair of terminals 156 and 157. The'terminal 157 is shown connected to a reference ground, for convenience, and the terminal 156 is connected over contacts of an on-off switch S2 to mechanical and electrical power supply elements here shown schematieally in FIG. 7 as a conventional DC power supply 158, and a conventional combined AC motor and transformer ACM. As will appear, the switch S2 is normally open, and is closed by a locator pin 159 when a cassette is inserted in the pocket 2 and the locator pin extends into the cassette to latch the cassette in the pocket.

The motor ACM may be of the conventional shaded pole induction type, having an energizing primary winding with a tap for energizing a projection lamp, to be described, and secondary windings connected to the DC power supply. These windings of the motor will be more particularly described below.

The output shaft 160 of the motor ACM drives a fan schematically indicated at 161, and also drives the input side 162 of a conventional electromagnetic clutch 163 having an output shaft 164. The shaft 164 is adapted to be driven from the shaft 160 through the clutch 163 when a clutch magnet CM is energized in a manner to appear. Another electromagnetic clutch, to be described below and not shown in FIG. 7, is driven by the shaft 160, for purposes to appear.

The fan 161 supplies air for cooling a projection lamp, to be described, and may also be used to supply air to the cassette to aid in drying the film after it is coated with processing composition.

The power supply 158 provides DC voltages for energizing various other elements of the apparatus, as will appear. In particular, the power supply 158 is connected over leads schematically indicated at 165 to control circuits schematically shown at 166.

The control circuits 166 at times supply energizing current for the clutch magnet CM over a lead 167. Control inputs are provided to the circuits 166 by switches and cams schematically indicated at 168, over leads generally designated 169. The control circuits 166 at times provide energizing current over a lead 173 to energize a cassette ejector disabling solenoid SL1. Other circuits, schematically indicated at 174, affect the operation of a film reel drive motor control circuit generally designated 175.

The shaft 164, driven by the motor ACM when the clutch magnet CM is energized, serves as the main programming shaft for directing the operation of the film drive, projection and audio recording and reproduction system under the influence of mechanical and electrical signals supplied by the cassette. Auxiliary shafts schematically indicated at l79 are driven by the shaft 164 as will be described in further detail below. A main cam shaft 180 is driven from the shaft 164 by means schematically shown in FIG. 7 as a pair of bevel gears 18]. An additional shaft 182 is driven by the shaft 164 synchronously with the shaft 180, to control the sound array in a manner to be described below.

The shaft 180 is supported in bearings schematically indicated at 183 and 184, fixed with respect to the plate 155. Carried on the shaft 180 are a number of cams, several of which control switches, to be described. In particular, the switches and cams 168 are driven by the shaft 180, and comprise a number of elements to be described below in conjunction with FIG. 13. Only those parts are shown in FIG. 7 which are conveniently displayed in fragmentary and schematic form, to illustrate the functional relationship between the elements of the system and indicate their relative location.

Two drive control cams 185 are symmetrically disposed on the shaft 180 and affixed thereto. These cams serve at times to drive a spingle plate 186 towards the wall 36.

The spindle plate 186 comprises a bar of metal or the like, provided with integral guide flanges 187 at its ends. The flanges 187 are slidable in ways, suggested at 188, formed integral with walls 189 and 190. i

The spindle plate 186 is normally urged to the position shown in H0. 7 by a pair of compression springs 191 located between the wall 36 and the spindle plate 186. When so moved by the cams 185, the spindle plate moves toward the wall 36, where it may be latched at times by a stop 192, as described in detail in the abovecited copending application Ser. No. 227,080. a

The motor control circuit 175 is also influenced by Also carried on the shaft 180 is a program disc 193 formed with three slots 194 disposed apart on the disc. These slots serve to locate program stops, as shaft angles on the cam shaft 180, by engagement with a detent schematically shown at 195. The detent 195 comprises an element 196 adapted to engage the slots 194, and urged into engagement therewith by a spring 197. The spring 197 extends between the element 196 and a support 198 fixed to the plate 155.

A blinder control cam 199 is disposed on the shaft 180 and affixed thereto. It is arranged to operate a blinder generally designated 200 through a cam follower 201 formed integral with the blinder 200 and adapted to engage the cam 199. This blinder and its operating mechanism are more fully described in the abovecite d US. application Ser. No. 227,080.

The blinder 200 at times interrupts the supply of light from a projection lamp Kl. The lamp K1 is disposed in a reflector generally designated 202 that is mounted on the plate to direct light from the lamp through the port 39, for admission to a cassette in the pocket 2.

A motor control cam 203 is mounted on the shaft and serves to control the position of the motor reversing switch MR. That relationship will be described below in more detail in connection with FIG. 14.

A snubber engaging cam 204 is fixed to the shaft 180. This cam at timesdrives a snubber stop 205 through the port 41 in the wall 36 for engagement with the snubber hub 82 in a cassette inserted in the pocket 2. The snubber stop 205 is normally urged back into the port 41 by means of a spring 206 acting between the wall 36 and a collar 207 formed on the snubber stop.

A cam 208 for controlling the position of the sound array 13 is mounted on the shaft 182 to be driven synchronously with the snubber control cam 204. The cams 204 and 208 may be shaped and orientated, in a manner to be described, so that the sound array and the snubber stop are engaged and disengaged simultaneously.

A drive sprocket 212 for the supply reel of a cassette in the pocket 2, and a drive sprocket 213 for the takeup reel, are mounted on the spindle plate 186. These drive sprockets are adapted to protrude through the ports 37 and 38 in the wall 36 when the spindle plate 186 is driven toward the wall 36 by the cams 185.

The sprocket 212 is formed integral with a shaft 214. A collar 215 is formed integral with the shaft 214. Another collar 216 is detachably secured to the shaft 214 by means schematically shown as cooperating threads formed on the parts. This collar 216 may be integral with a splined extension 217 that engages corresponding splines 218 formed in a cylindrical bore in the end of a drive shaft 219.

The shaft 214 and the collars 215 and 216 cooperate with bearings schematically indicated at 220, mounted in the spindle plate 186 to allow the shaft 214 to rotate in the spindle plate, while preventing it from being translated along the axis of the shaft 214 with respect to the plate 186. The splines 218 and the splined extension 217 cooperate to allow the shaft 214 to be driven by the shaft 219, while allowing relative translational motion between the shafts 214 and 219. Thus, the shaft 214 may be fixed relative to the base plate 155 against translational motion, while rotatable with respect thereto. 

1. Film transport and illumination apparatus for a sound motion picture system utilizing strip film on which visual images and a sound track can be recorded, comprising incremental drive means operable to move the film strip past an optical station in increments corresponding to image frames, a capstan operable to move the film past a sound station at a substantially uniform speed dependent on the rate of rotation of said capstan, an induction motor having a stator and an output shaft, means connecting the output shaft of said induction motor to said incremental drive means to operate said drive means at a rate determined by the speed of said shaft, a primary winding on said stator, a secondary winding on said stator, a projection lamp connected in series with at least a portion of one of said windings, means for connecting a source of alternating current to said primary winding, a direct current motor having a winding and an output shaft, speed reduction means drivingly connecting the output shaft of said direct current motor to said capstan, direct current power supply means having first, second and third output terminals and input terminals energized by said secondary winding for producing first and second direct voltages, said first direct voltage being produced between said first and said third output terminals and said second direct voltage being produced between said second and said third input terminals, a first resistor connected in series with the winding of said direct current motor between said first and said third output terminals, a transistor having an emitter and a collector connected in parallel with said resistor, said transistor having a base, a first filter capacitor connected between the base and the collector of said first transistor, a second transistor having a collector, an emitter and a base, the collector and the emitter of said second transistor being connected between said second terminal and the base of said first transistor, a second resistor connected between the base of said second transistor and said third output terminal, a second filter capacitor connected between the base of said second transistor and said second output terminal, a photocell connected in parallel with said second filter capacitor, light source means for illuminating said photocell along a path adapted to be interrupted by a loop of film formed between said drive means when said uniform speed differs from the average speed of the film produced by said incremental drive means, whereby the resistance of said photocell is modulated at the rate of operation of said incremental drive means to modulate the amount of current flowing between the emitter and the collector of said second transistor at a rate determined by the capacitance of said second filter capacitor and thereby modulate the bias on said first transistor at a rate determined by the capacitance of said first filter capacitor, said capacitors and said speed reduction means being selected to make the response time of said capstan long relative to the rate of operation of said incremental drive means.
 2. In combination with a sound motion picture system having a film drive pawl driven by an induction motor at a relatively fixed rate to move a strip of film incrementally past a projection station and a projection lamp at said projection station energized by a winding on said induction motor, a sound drive system for driving the strip of film through a sound station at uniform speed, comprising capstan means adapted to engage the film, a DC motor for driving said capstan means at a speed determined by the amount of current supplied to said DC motor and a motor speed control circuit for said DC motor comprising a source of voltage, a fixed resistor connected between said DC motor and said source to supply a first component of current to said DC motor to operate said capstan means at a speed causing film motion below the average film speed produced by said film drive pawl, first amplifying means responsive to a first applied signal to supply additional current to said DC motor in amounts determined by said first applied signal, first filter means for damping changes in the amplitude of a signal applied to said first amplifying means, second amplifying means responsive to a second applied signal to apply a first signal to said first amplifying means, second filter means for damping changes in the amplitude of a signal applied to said second amplifying mEans, and sensing means responsive to the length of a strip of film between said stations for applying a second signal to said second amplifying means fluctuating at said rate of operation of said film drive pawl.
 3. A film transport system for moving a strip of motion picture film uniformly past a sound station and incrementally past a projection station, comprising capstan means located at said sound station and adapted to engage the film and move it through said sound station when said capstan means is driven by a shaft at a speed determined by the speed of the shaft, a DC motor having a shaft connected to said capstan means, an induction motor having an output shaft and an energizing winding, incremental film transport means located at said projection station, connected to the output shaft of said induction motor and adapted to engage the film and move it incrementally through said projection station at an average speed determined by the speed of said induction motor output shaft, circuit means for supplying alternating current to the energizing winding of said induction motor, sensing means located between said stations and responsive to the length of the film between said stations for producing a control signal in accordance with said length that fluctuates at the frequency of operation of said incremental drive means, and two stage amplifying means controlled by said signal for supplying direct current to said DC motor at a rate tending to keep the average length of the film between said stations constant, a first stage of said amplifying means comprising filter means for damping fluctuations in said signal with a first variable time constant, and a second stage of said amplifying means comprising means for damping the damped signal from said first stage with a time constant substantially greater than the maximum time constant of said first stage.
 4. The apparatus of claim 3, in which said sensing means comprises a radiation responsive impedance and means for irradiating said radiation responsive impedance over a path interrupted by a length of film between said stations greater than a predetermined length.
 5. The apparatus of claim 4, in which said first stage comprises a source of DC voltage, a resistor, a capacitor, and an amplifying device having a pair of load terminals and a control terminal, said source having terminals connected in series with said radiation responsive impedance and said resistor, said capacitor being connected in parallel with said radiation responsive device, and means connecting one load terminal and the control terminal of said amplifying device in parallel with said capacitor, whereby said first time constant is determined primarily by said capacitor, said resistor and said radiation responsive impedance, and the other of said load terminals and one terminal of said source comprise output terminals for applying said damped signal to said second stage.
 6. The apparatus of claim 4, in which said second stage comprises a source of DC voltage, a resistor, a capacitor, and an amplifying device having a pair of load terminals and a control terminal, said source having terminals connected in series with said DC motor and said resistor, the load terminals of said amplifying device being connected in parallel with said resistor, and said cpacitor being connected between a first of said load terminals and said control terminal, said second time constant being determined in part by said capacitor, and said control terminal and one of said load terminals comprising input terminals to which the damped signal from said first stage is applied.
 7. The apparatus of claim 4, in which said first stage comprises a first source of DC voltage, a first resistor, a first capacitor, and a first amplifying device having a pair of load terminals and a control terminal, said first source having terminals connected in series with radiation responsive impedance and said first resistor, said first capacitor being connected in parallel with Said radiation responsive device, and means connecting one load terminal and the control terminal of said first amplifying device in parallel with said first capacitor, whereby said first time constant is determined by said first capacitor and said radiation responsive impedance, the other of the load terminals of said first amplifying means and one terminal of said first source comprising output terminals for applying said damped signal to said second stage, and in which said second stage comprises a second source of DC voltage, a second resistor, a second capacitor, and a second amplifying device having a pair of load terminals and a control terminal, said second source having terminals connected in series with said DC motor and said second resistor, the load terminals of said second amplifying device being connected in parallel with said second resistor, and said second capacitor being connected between a first of the load terminals and the control terminal of said second amplifying device, said second time constant being determined in part by said second capacitor, and the control terminal and one of the load terminals of said second source comprising input terminals of said second stage to which said output terminals of said first stage are connected.
 8. A sound motion picture system, comprising means forming a projection station at a first location, a projection lamp located at said projection station, a film drive claw located at said projection station, means forming a sound station at a second location, a film drive capstan located at said sound station, means for guiding a strip of film over a path from said capstan to said claw, said path including a region in which the film is free to form a loop of variable length, an induction motor, means operated by said motor for driving said claw, capstan drive means comprising a DC motor for driving said capstan at a speed determined by an applied current, said induction motor comprising a set of windings linked by a common core, means connecting at least a part of one of said windings in series with said lamp, first and second input terminals connected to one of said windings and adapted to be excited by an alternating voltage to cause the excitation of all of said windings, means responsive to the length of a loop of film in said region for producing an output signal in accordance with said length and fluctuating at the rate of operation of said film drive claw, means connected to one of said windings for producing a DC voltage, means controlled by said DC voltage for producing a component of current adequate to drive said DC motor at a speed below the speed required to move film at the average rate at which film is moved by said drive claw, first amplifying and filtering means controlled by said output signal for producing a damped control signal in accordance with said output signal but fluctuating at a first lower rate than said output signal, second amplifying and filtering means controlled by said DC voltage and said damped control signal for producing a control current component in accordance with said damped control signal but fluctuating at a second rate lower than said first lower rate, and circuit means for applying the sum of said current components to said DC motor.
 9. A sound motion picture system, comprising means forming a projection station at a first location, a projection lamp located at said projection station, a film drive claw located at said projection station, means forming a sound station at a second location, a film drive capstan located at said sound station, means for guiding a strip of film over a path from said capstan to said claw, said path including a region in which the film is free to form a loop of variable length, an induction motor, means operated by said motor for driving said claw, capstan drive means comprising a DC motor for driving said capstan at a speed determined by an applied current, said induction motor comprising a set of windings linked by a comMon core, means connecting at least a part of one of said windings in series with said lamp, first and second input terminals connected to one of said windings and adapted to be excited by an alternating voltage to cause the excitation of all of said windings, means connected to one of said windings for delivering an applied current to said DC motor, said applied current delivering means including means responsive to the length of a loop of film in said region for delivering an applied current to said DC motor selected to cause said capstan to drive the film at a speed below the average speed of the film being produced by said film drive claw when the length of a loop of film in said region is greater than a predetermined length and for delivering an applied current to said DC motor selected to cause said capstan to drive the film at a speed above the average speed of the film being produced by said film drive claw when the length of a loop of film in said region is greater than the predetermined length.
 10. The system of claim 9 wherein said applied current delivering means additionally includes means for making the time of response of said capstan to changes in the length of the film loop in said region long relative to the rate of operation of said film drive claw. 